There is often a need or a desire to permit the digital electronic communication between two or more digital electronic apparatus. For example, it is often desirable to have a personal computer interfaced with a local area network (LAN). To implement the digital electronic communication between the computer and the network, various communication protocols have been developed. For example, Ethernet is a common communication protocol used in many local area networks.
In practice, in order to network a personal computer, a network card is installed in the computer. Often, the network card includes an Ethernet port. A cable assembly, typically including Ethernet connectors at both ends, can be used to connect the Ethernet port of the network card into the network system.
A problem can sometimes arise when two or more apparatus are configured to communicate with different communication protocols. For example, laptop computers are not often provided with Ethernet cards, and therefore cannot directly communicate with Ethernet networks or other apparatus communicating using Ethernet protocols. One solution is to add a PCMCIA Ethernet card to the portable computer to allow its connection to an Ethernet network. However, standard PCMCIA Ethernet cards have considerable associated overhead from both a hardware and a software point of view. Further, the speed of the Ethernet connection is limited by the speed of the PCMCIA interface. External devices that add Ethernet capabilities to lap-tops undesirably add size and weight to the overall system.
This communication problem will be further explained with reference to FIGS. 1A–1C. In FIG. 1A, a first apparatus 10 is coupled to a second apparatus 12 by a cable assembly 14. Apparatus 10 can be, for example, a personal computer provided with a network card 16 having an Ethernet port (connector) 18. The apparatus 12 can be any number of other types of computer equipment including a network hub, a personal computer, a printer, etc., and is provided with its own network card 20 with Ethernet port (connector) 21. It should be noted that the circuitry of network cards 16 or 20 can be integrated into the electronics of the apparatus 10 or 12, respectively. For example, the circuitry of network card 16 can be provided on the mother board of a personal computer apparatus 10.
The cable assembly 14 includes a first connector 22, a second connector 24, and a cable 26 extending between the two connectors. Connector 22 engages with connector 18 of Ethernet card 16, and connector 24 engages with connector 21 of Ethernet card 20. Since both apparatus 10 and apparatus 12 are communicating with the same communication protocol, i.e. with an Ethernet protocol, a simple connection by cable assembly 14 suffices to place the two pieces of apparatus into digital electronic communication.
A problem arises when two apparatus attempt to communicate using two different communication protocols. For example, in FIG. 1B, it may be desirable to have a first apparatus 10 communicate with a second apparatus 12 which communicates by a different communication protocol. That is, the apparatus 10 might be provided with an Ethernet ported network card 16 while apparatus 12 might be provided with a serial communications (e.g. an RS-232) card 28. In such instances, a translator box 30 can be provided which communicates with an Ethernet communication protocol at a first port 32 and with a serial communication protocol at a second port 34. Devices including interface cards are examples of such translator boxes 30.
In FIG. 1C, a first apparatus 10 is coupled to a second apparatus 12 by a “smart” cable 36. In an example, the apparatus 10 has a card 38 communicating with a first communication protocol, and apparatus 12 has a card 40 communicating with a second communication protocol. However, instead of having a separate translator box 30 as explained with reference to FIG. 1B, the smart cable 36 of FIG. 1C includes embedded circuitry for translating the communication protocol of apparatus 10 into the communication protocol for apparatus 12. For example, apparatus 10 can be a personal computer having a USB card 38 and apparatus 12 can be a printer having a parallel or Centronics card 40. The smart cable 36 then translates the USB protocols of apparatus 10 into Centronics protocols of apparatus 12 and vice versa. The digital circuitry of the smart cable can be located within a connector 42 or a connector 44 of the cable or can be part of the cable 46, e.g. in the form of a dongle 48.
There are several examples of smart cables that are commercially available. For example, Methode New England provides smart cables with built-in termination, hot swap circuitry, and dongle integration. The Smart Cable Company of Tacoma, Wash. produces a FC819/825 smart serial to parallel cable which automatically adjusts itself for serial to parallel or parallel to serial conversion. Logic Control, Inc. markets the IW 2000 Intelligent Wedge Cable which converts RS232 or decoded TTL serial data to keyboard data. Also, B&B Electronics Manufacturing Company markets the model USBP10 cable which allows USB ports to be coupled to parallel printers.
The problem with the current generation of smart cables is that they are only available for a limited number of rather simple protocol conversions, and they are not easily upgradable. Also, many of these devices require software drivers to be loaded onto a host computer in order to operate properly. Further, most of these devices require either a relatively large connector (such as Centronics connector), or a bulky dongle, to house the translation circuitry. This is because the translation circuitry as associated printed circuit (PC) board tends to be quite bulky.
In addition, even “smart” cables are not typically “plug-and-play.” That is, typically drivers are required on the host computer to which the cable is attached to properly operate the smart cable. Therefore, the smart cables of the prior art tend not to be “transparent” from the user's point of view.